1. Field of the Invention
The present invention relates to a syringe, and more particularly, to a disposable syringe. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for providing a safer disposable syringe with enhanced safety measures.
2. Discussion of the Related Art
Generally, a syringe is a medical device used to inject an injection liquid (e.g., medication) into the body (or veins) of a medical patient. Also, the syringe is typically disposable after use, thereby preventing a third person from being infected by diseases carried by the patient. A related art disposable syringe will now be described with reference to the accompanying drawings.
FIG. 1 illustrates an exploded perspective view of a disposable syringe according to a first embodiment of the related art.
Referring to FIG. 1, the related art disposable syringe is formed of a cylinder 1 having an empty space therein, and a coupling tube 2 formed at a fore end of the cylinder 1 and having a step difference. The related art disposable syringe also includes a plunger 3 moving within the cylinder 1 in back-and-forth movements along the length of the cylinder 1. A piston 4 is formed at the fore end of the plunger 3 and moves along with the plunger 3 in airtight contact with the inner surface of the cylinder 1.
A syringe needle holder 5 is detachably fixed onto the external surface of the coupling tube 2 formed on the cylinder 1. A syringe needle 6 is fixed in the syringe needle holder 5. Also, a protective cap 7 is attached to completely cap the syringe needle holder 5 and the syringe needle 6.
FIG. 2A illustrates an exemplary process step of sucking the injection liquid into the syringe.
Referring to FIG. 2A, the protective cap 7 protecting the syringe needle 6 is first detached from the syringe needle holder 5. Then, the plunger 3 inserted into the empty space of the cylinder 1 is pushed forward to the fore end of the cylinder 1. Then, the end of the syringe needle 6 is inserted and dipped into an injection liquid container (not shown). Thereafter, the plunger 3 having the piston 4 fixed thereon is pulled back, thereby creating a suction force within the empty space of the cylinder 1. Due to the suction force, the injection liquid is sucked into the cylinder 1 through the syringe needle 6 fixed to the syringe needle holder 5, thereby filling the empty space of the cylinder 1.
FIG. 2B illustrates an exemplary process step of injecting the injection liquid to a patient.
Referring to FIG. 2B, a user sticks the syringe needle 6 into a patient's skin, and then pushes the plunger 3 to move the piston 4 towards the fore end of the cylinder 1. At this point, a pressure is formed within the empty space of the cylinder 1, more specifically, at the fore end of the piston 4 (shown as the left side area in FIG. 2B). Accordingly, due to the pressure of the piston 4, the injection liquid filled in the empty space of the cylinder 1 flows out of the cylinder 1 through the coupling tube 2 formed at the edge of the cylinder 1.
The injection liquid passing through the coupling tube 2 then continues to flow through the syringe needle 6 fixed in the syringe needle holder 5, thereby being injected into the skin and veins of the patient. During this process, because the syringe needle holder 5 is fixed to the coupling tube 2 by interference fit, the injection liquid does not leak from the coupling tube 2 and the syringe needle holder 5.
Meanwhile, after the use of the syringe, the protective cap 7 is safely and completely fixed to the syringe needle holder 5 to cap and protect the syringe needle 6, so as to safely dispose of the used syringe.
The above-described disposable syringe is advantageous in that the injection liquid does not leak from the syringe during the injection process. However, when recapping the protective cap 7 onto the syringe needle holder 5 after use, the user or a third person may be injured by the syringe needle. Also, when the protective cap is detached from the syringe while disposing medical waste, another third person (i.e., a person handing the medical waste) may also be injured by the syringe needle.
Therefore, in order to prevent such small accidents from occurring, manufacturers of medical instruments, apparatuses, and devices are developing new types of disposable syringes with enhanced safety functions.
FIG. 3 illustrates an exploded perspective view of a disposable syringe according to a second embodiment of the related art.
The related art syringe includes a cylinder 11 having a coupling tube 12 formed to have a step difference at the fore end edge of the cylinder 11, and a plunger 13 having a piston 14 fixed thereto. An O-ring 19 is formed at the inner circumference of the coupling tube 12 to be fixed airtight to the syringe needle holder 15. Also, a flange 15a is formed at the back end and on the outer circumference of the syringe needle holder 15.
The cylinder 11 is formed to have one end and the other end connected to each other and forming an empty space therein. The coupling tube 12 having a step difference is formed at the fore end of the cylinder 11. Finally, a protective cap 17 is detachably fixed to the outer surface of the coupling tube 12, so as to cap and protect the syringe needle 16.
The plunger 13 moving within the cylinder 11 in back-and-forth movements along the length of the cylinder 11 is inserted into the empty space of the cylinder 11. The piston 14 is formed at the fore end of the plunger 13, so as to move along the cylinder 11 in airtight contact with the inner surface of the cylinder 11, thereby providing pressure or a suction force. In addition, a connecting part 13a corresponding to a connective projection of the syringe needle holder 15 is formed at the fore end of the plunger 13. Finally, a cutting grove 18 is formed on the plunger 13 near the piston 14, thereby enabling the plunger 13 to be easily broken.
The syringe needle holder 15 is inserted into the cylinder through the empty space, so as to be exposed to the fore end of the coupling tube 12. In order to be more stably fixed to the coupling tube 12, a contacting surface should be maintained between the syringe needle holder 15 and the coupling tube 12. However, if the syringe needle holder 15 is fixed to the coupling tube 12 by interference fit, the syringe needle holder 15 may not be able to be pulled into the empty space of the cylinder after the injection. Therefore, a fine gap should be maintained when fixing the syringe needle holder 15 to the coupling tube 12. Due to the step difference between the cylinder 11 and the coupling tube 12, the flange 15a comes into contact with the inner step formed inside the cylinder 11.
The O-ring 19 is fixed to the inner circumference of the coupling tube 12, thereby preventing injection liquid from leaking through the fine gap between the coupling tube 12 and the syringe needle holder 15. More specifically, the O-ring 19 maintains an airtight seal between the coupling tube 12 and the syringe needle holder 15.
FIG. 4 illustrates a perspective view of a syringe needle holder and the plunger being detached from the disposable syringe according to the second embodiment of the related art.
A pair of projections 15b facing into each other is formed in the inner circumference and at the back end of the needle holder 15. A connecting part 13a is formed at the fore end of the plunger 13, so as to be connected with the projections 15b when the plunger 13 is pushed to the fore end of the cylinder 11. Also, each of the connecting part 13a and the projections 15b has an inclined surface, so as to minimize interference caused by contact when the fore end of the plunger 13 is inserted to the syringe needle holder 15.
FIGS. 5A to 5E illustrate cross-sectional views showing usage steps of the disposable syringe according to the second embodiment of the related art.
In order to inject the injection liquid to a patient, the injection liquid should first be sucked onto the empty space of the cylinder. However, since the process step of sucking the injection liquid into the syringe is the same as that described in FIG. 2A, the description will be omitted for simplicity.
FIG. 5A illustrates the empty space of the cylinder 11 is filled with an injection liquid, shown as the left side area of the syringe. The process of injecting the injection liquid to the patient is identical to that described in FIG. 2B, and therefore, the description of the same will also be omitted for simplicity.
FIGS. 5B and 5C illustrate the completion of the injection and the process step of pulling the syringe needle holder back into the cylinder.
Referring to FIGS. 5B and 5C, when the injection of the injection liquid is completed, the syringe needle holder 15 is inserted in the coupling tube 12 formed on the cylinder 11. At this point, the flange 15a, which is formed at the back end and on the outer circumference of the syringe needle holder 15, comes into contact with the inner step formed inside the cylinder 11 due to the step difference between the cylinder 11 and the coupling tube 12. And so, the flange 15a limits further forward movement of the syringe needle holder 15.
Meanwhile, after the injection is completely, the syringe needle 16 is pulled out of the patient's skin. Then, the plunger 13 is pulled back in the direction opposite to the patient (i.e., in a backward direction), the syringe needle holder 15 is also pulled back along with the plunger 13. This is because the connecting part 13a is connected to the projections 15b of the syringe needle holder 15.
Then, the plunger 13 is pulled further towards the back end of the cylinder 11, so that the syringe needle holder 15 is completed pulled into the cylinder 11. The syringe needle holder 15 is held by the connecting part 13a of the plunger 13. In other words, since the outside diameter of the flange 15a is smaller than the inside diameter of the cylinder 11, the syringe needle holder 15 is hung onto the fore end of the plunger 13. Therefore, due to an eccentric center of gravity, the syringe needle holder 15, having the connecting point between the holder 15 and the fore end of the plunger 13 as its support point, is inclined downwards (i.e., towards the gravitational direction). At this point, only the fore end of the syringe needle 16 comes into contact with the inner surface of the cylinder 11. Moreover, a constant inclination angle is maintained between the contacting surface of the cylinder 11 and the syringe needle holder 15.
FIGS. 5D and 5E illustrate process steps of preventing the syringe needle holder from being extracted from the cylinder.
Referring to FIGS. 5D and 5E, the cutting groove 18 formed on the plunger 13 is pulled back near the outside of the cylinder 11. Then, the plunger 13 is repeatedly pressed downwards in a direction perpendicular to the plunger 13, thereby breaking the plunger 13 along the cutting groove 18 formed thereon. Subsequently, the broken portion of the plunger 13 is placed to be parallel to and facing into the fore end of the cylinder 11. Then, when the broken portion of the plunger 13 is inserted through the coupling tube 12, the fore end of the cylinder 11 is blocked, thereby preventing the syringe needle holder 15 held within the cylinder 11 from falling or slipping out of the cylinder 11.
However, the above-described related art disposable syringe is disadvantageous in that it requires and uses an O-ring.
The O-ring is sensible to even the slightest external pressure, thereby being easily deformed. Therefore, when the O-ring fails to be stably inserted into the coupling tube, the syringe can become deficient.
Also, in order to reduce deficiency in disposable syringes using the O-ring, a wide range of complex auxiliary fabrication devices are required in the fabrication line, thereby causing an increase in the product cost.
Finally, since the deficiency in the O-ring cannot be recognized through the naked eye, when using a syringe fabricated with the deficient O-ring, the injection liquid may leak from the syringe during the injection process.